This application claims the priority of 196 28 333.7, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a transfer device, and more particularly, to a transfer device for transfer of workpieces between press stations along a given transfer direction, comprising supporting and guiding devices which extend essentially along the transfer direction and which carry therebetween cross transverses equipped with gripping devices arranged to be engaged with and disengaged from the workpieces, and driving devices configured to act upon the gripping devices for swivelling the gripping devices about an axis of rotation transverse to the transfer direction.
In press systems having several press stations which are arranged behind one another along a parts passage route, transfer devices are provided which remove the corresponding sheet metal parts from the press stations and supply them in a timed manner to the respective press station which follows. Intermediate depositing devices are usually provided between the individual press stations so that the workpieces to be transported can temporarily be deposited thereon to permit a reduction of the transfer step width. For carrying out the transfer, a transfer device is used which grips the workpieces when the tool is open and, in a transfer movement during which a lifting movement is superimposed on a horizontal transfer movement, guides them out of the tool or inserts them therein. Thereby, a vertical lowering or depositing movement is superimposed on the transfer movement.
Particularly with workpieces which have complicated designs and/or workpieces which are to be placed in the tools obliquely, i.e., deviating from a horizontal plane, it may be necessary, during, for example, the guiding out of or guiding into the tool, to swivel the workpiece about a transverse axis. In the case of corresponding tool and workpiece shapes, this transfer may become necessary in order to avoid a collision between the sheet metal part and the tool during the transfer movement. The first machining station of press systems, optionally also a machining station which follows, is configured as a drawing station. The further machining may require an oblique position of the sheet metal part in the bottom tool. On one hand, for example, because of the high lift numbers, the lifting-out lift cannot be selected to be arbitrarily large. On the other hand, it is necessary to guide low-placed drawn surfaces which are bent by deep-drawing freely past above the form of the bottom tool.
A conventional transfer device is shown in EP-A-0 499 901 and includes two guide rails which extend in the transfer direction. The guide rails are arranged on the right and the left side next to the tools of the press stations, travelling carriages being disposed on these guide rails. The guide rails are connected with a lifting and lowering unit in order to carry out a targeted horizontal movement. The travelling carriages are connected with a transfer drive unit in order to be moved along the travelling rails in a targeted manner. Each cross traverse is arranged between two carriages and is rotatably on the end side disposed on the carriages. As gripping devices for gripping and holding sheet metal parts, the cross traverse carries a suction spider which has a number of suction feet which can be acted upon by a vacuum. In order to be able to swivel the suction spiders about a transverse axis, the corresponding cross traverse is connected on the end side by a coupling with a swivel lever which can be swivelled with a driving cylinder provided on the carriage.
In order to limit the usability of the transfer device not to applications in which rotational movements of the workpieces are required in only one or in a few stations, all carriages must be equipped with corresponding rotating units. This makes the construction more complicated and increases the weight of the transfer device and particularly of the carriages. Correspondingly high accelerating and braking forces are thus applied which is disadvantageous with respect to energy consumption. Furthermore, the known construction requires considerable space which reduces the permissible lifting height of the cross traverse transfer system. The known transfer device is unlike the ideal transfer design which could handle a plurality of workpieces so that it can also be set up for future tasks which cannot be predicted in detail.
JP 62-142431 describes a transfer device with a support carrying the suction spider and, as a whole, is rotatably disposed on a rotating unit. The rotating unit is held on a support which can be moved vertically up and down as well as horizontally.
If a corresponding transfer device is to have several such transverse supports, a rotating unit is required at each transverse support position irrespective of whether, for the concrete individual case and at the respective position, a swivel movement of the suction spider is actually required. This affects the constructive expenditures and the weight of the transfer device.
An object of the present invention is, therefore, to provide a transfer device which permits a high variability.
This object has been achieved in accordance with the present invention by a transfer device at least one of the cross traverses carries a bearing device on which the associated gripping device is operatively disposed to be swivelled about the axis of rotation, and this at least one cross traverse is configured to carry the driving device for swivelling the gripping device.
The cross traverses, which have a rigid construction per se, carry suction spiders which are each rotatably disposed thereon. The cross traverse also carries the driving device, such as a geared motor, hydraulic or pneumatic drives and the like which, as required, swivel the gripping devices. Thus, cross traverses with swivellable gripping devices can be provided at positions of the transfer device which constructionally correspond to those positions which are developed for cross traverses with non-swivellable gripping devices.
Regardless of whether the corresponding cross traverse carries swivellable gripping devices or not, the end-side suspension of the cross traverses has a uniform construction. No rotating units are required which act upon the ends of the cross traverses and which would have to be fixedly provided on the supporting and guiding devices, for example, on travelling carriages disposed on travelling rails. This permits the fast exchange of cross traverses with rotatable gripping devices for cross traverses with non-swivellable gripping device and viceversa. The constructive and economic expenditures are therefore reduced to the respective required extent for each application. Simultaneously, the transfer devices offers a high measure of variability and permits a fast adaptation to different, also future transfer tasks which presents no problems.
Because driving devices acting upon the gripping devices are to be provided only at such positions or cross traverses at which they are actually necessary, the mass of the transfer device which is to be accelerated and braked is not increased by unnecessary driving devices which are to be moved along. A fast transfer and a lowering of the driving/braking power are thereby permitted.
The swivellable bearing of the gripping devices on the cross traverse and the assignment of a driving device carried by the cross traverse to each gripping device provides the basis for the fact that gripping devices provided on one and the same cross traverse are divided into gripping units which are to be controlled or swivelled differently. For example, on one cross traverse, a first and second suction spider may be provided of which only one is swivelled or which are swivelled differently. Thus, sheet metal parts can be handled which are to be swivelled differently and which are to be transported through the press stations side-by-side. This may become necessary if two separate sheet metal parts which have different shapes are formed from one sheet bar.
As a result, the versatility of the transfer device according to the present invention even makes it possible that a sheet metal part which, as a cutout for forming a large opening in another sheet metal part, was separated from the latter can be synchronously conveyed together therewith and can be shaped into a separate part. It can be held, transported and changed into different tilting angles by a separate suction spider which is disposed on the same cross traverse as the suction spider for the surrounding larger part.
A coupling arrangement between the cross traverse and the gripping devices or a gripping unit formed of gripping devices, a bearing device and driving devices can, as required, permit the release of the gripping unit from the cross traverses so that the cross traverses can be retrofitted for a respective application. In particular, swivellable gripping devices/units can be exchanged for non-swivellable gripping devices/units.
The axis of rotation of the gripping devices is preferably situated within the cross traverse, and the center of gravity of the workpiece is situated below the cross traverse. Consequently, no significant torque is created by the force of the weight of the workpiece which would act upon the driving devices.
In a construction type which can be easily retrofitted manually, the bearing device includes at least one divided bearing unit which has two curved guiding surfaces on which the gripping devices are disposed by way of rollers. A gear wheel segment is used for the coupling with a geared motor serving as the driving device and can also be considered to be a bent toothed rack. This construction permits a particularly low height of the swivellable gripping unit which is no larger or hardly larger than that of the non-swivellable unit. This does not limit the permissible vertical lift of the transfer device.